Add EditorConfig for code styling

[Turnerj]

See: https://docs.microsoft.com/en-us/visualstudio/ide/editorconfig-code-style-settings-reference

It will be very good idea. Because my code style settings differs, and there are many problems, when i proposed pull requests earlier...

[Turnerj]

@rus-bit , yep, or even just between different computers I work on. People have to deal with different formatting for different projects and something like an editor config file definitely reduces the barrier for entry.

Hope to get this sorted in the next few days.

[Turnerj]

I've added an editor config file based on the one in the Roslyn repo.

There isn't anything too crazy in it. From my experience, most of the settings are what I had when I installed VS2017 cleanly. (eg. tabs over spaces for C#, braces on new lines)

The one rule I do specify in it explicitly is in regards to casing for "Non-field Members". From various different C# projects I have seen, some have theirs as camel case and some as pascal. I've made the decision to have mine follow pascal case.

I may change and tweak this in the future but basically follow the suggestions it highlights and let it do the document formatting.